It has been often the case that, in an armrest device to be installed to a seat of automobile, and the like, the armrest (or elbow rest) is made rotatable upward/downward so that it does not interfere with a passenger when he or she sits on the seat or stands up therefrom.
Moreover, it has been carried out to make such an armrest adjustable in the angular position in the up/down rotation so as to make the armrest likely to be used in compliance with users' bodily shape, and so forth.
As a mechanism for that, many have been heretofore employing conventionally a type in which a metallic torsional coiled spring is used as a unidirectional locking spring that allows the upward rotation of armrest body but prohibits the downward rotation.
One being classified with this type is made as follows: a locking spring is inserted into a stationary axial supporter in a seat; one of the ends is fixed to an armrest body so as to make the other end into being a free end; and the locking spring contracts diametrically to tighten the axial supporter up when a user tries to rotate the armrest body downward, thereby prohibiting the downward rotation of the armrest body by the frictional force between the locking spring and the axial supporter; whereas the locking spring expands diametrically and then the locking spring rotates integrally with the armrest body around the axial supporter when he or she rotates the armrest body upward, thereby allowing the upward rotation of the armrest body.
For example, armrest devices using locking springs of this sort are disclosed in Patent Literature No. 1, Patent Literature No. 2 and Patent Literature No. 3 below.
However, in the case of armrest devices being classified with this type, the following problems arise: not only the operation has become heavy upon operating the armrest to rotate because a metallic and large-sized locking spring with heavy weight is used so that the resulting armrest device itself has turned into one with heavy weight; but also it is difficult to meet the request of weight saving especially when being used in the application for a seat of automobile for which weight saving has been strongly required recently.
Meanwhile, in addition to those being classified with a locking-spring type like above, one utilizing a ratchet mechanism has been conventionally known heretofore publicly, ratchet mechanism which is utilized to allow the armrest body to rotate upward but to prohibit it from rotating downward.
For example, ratchet-style armrest devices of this sort are disclosed in Patent Literature No. 4 and Patent Literature No. 5.
One being classified with this type comprises: an armrest body to be installed rotatably upward/downward with respect to a seat at the base end; a ratchet mechanism comprising stationary-side first ratchet teeth being disposed around the axial line of the rotation of the armrest body, and movable-side second ratchet teeth being disposed in such a state as facing the first ratchet teeth as well as in such a state as rotating integrally with the armrest body, meshing with the first ratchet teeth so as to be inhibited from moving in the downward rotary direction of the armrest body, and getting over the first ratchet teeth so as to be movable in the upward rotary direction thereof; and an urging member for urging the first ratchet teeth and second ratchet teeth in such a direction as they press one another; wherein an angular position upon making use of the armrest body is made adjustable by means of that ratchet mechanism.
This armrest device is moreover equipped with the following: a releasing mechanism for separating the first ratchet teeth and second ratchet teeth away from each other so as to release the meshing; a retaining mechanism for retaining the first ratchet teeth and second ratchet teeth, which have been separated away from each other, in a separated state, thereby allowing the downward rotation of the armrest body; and a returning mechanism for undoing the retainment by means of the retaining mechanism to relatively move the first ratchet teeth in such a direction as approaching the second ratchet teeth, thereby returning them to the meshing.
By doing thusly, it becomes feasible to change the angular position of the armrest body from an upper-side position to a lower-side position, and hence to adjust it.
In the case of an armrest device being classified with this ratchet style, it is feasible to make the armrest device lightweight compared with one being classed with the aforementioned locking-spring style, because it is not necessary to use any metallic locking spring whose weight is heavy compared with one being classified with a locking-spring style; moreover, because it is feasible to make a member comprising the first ratchet teeth and another member comprising the second ratchet teeth of resin, respectively (making these of resin is disclosed in Patent Literature No. 4).
However, in the case of conventional armrest devices being classified with a ratchet style of this sort, involving those being disclosed in these Patent Literature No. 4 and Patent Literature No. 2, since a ratchet member comprising the stationary-side first ratchet teeth, and another ratchet member comprising the movable-side second ratchet teeth are constituted of distinctive members, which are made separately from or independently of the armrest, respectively, they have problems like below that come with this construction.
Specifically, the quantity of component parts gets greater because a first ratchet member and a second ratchet member are needed as those for constituting the ratchet mechanism, respectively. Moreover, since the drawback results in entailing an assembly step of assembling one of the ratchet members with the armrest body, the required assembly man-hour requirement has got greater, and thereby costs have become higher as being accompanied by this drawback.
Furthermore, since a large load, which is applied to the armrest, acts onto the assembled section when assembling one of the ratchet members with and then fixing it to the armrest body, the connection strength at the assembled section should be of high strength.
In order to do that, it is effective to make the armrest body and one of the ratchet members as a fit-combined structure so as to receive forces physically at the fit-combined section. However, if such is the case, since a structure for fitting them together, and a space for that should be provided, these drawbacks entail such a drawback that the assembled section has become large-sized between the ratchet mechanism and the armrest body.
In addition, if rattling should have occurred at the assembled section when such an assembly structure is made, there might possibly arise such a fear that the armrest body rattles about when a user applies a load to the armrest body. Then, that drawback has hindered the armrest body from moving smoothly, and moreover has deteriorated the feeling of using the resulting armrest.    Patent Literature No. 1: Japanese Patent Gazette No. 4,089,386;    Patent Literature No. 2: Japanese Patent Gazette No. 4,094,421;    Patent Literature No. 3: Japanese Patent Gazette No. 4,087,635;    Patent Literature No. 4: Published Japanese Translation of PCT Application Gazette No. 2003-520, 156; and    Patent Literature No. 5: Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2007-283, 908